title: Placenta growth factor induces 5-lipoxygenase-activating protein to increase leukotriene formation in sickle cell disease.
abstract: Individuals with sickle cell disease (SCD) have increased inflammation, a high incidence of airway hyperreactivity (AH), and increased circulating leukotrienes (LT). We show that expression of 5-lipoxygenase and 5-lipoxygenase activating protein (FLAP), key catalytic molecules in the LT pathway, were significantly increased in peripheral blood mononuclear cells (MNCs) in patients with SCD, compared with healthy controls. Placenta growth factor (PlGF), elaborated from erythroid cells, activated MNC and THP-1 monocytic cells to induce LT production. PlGF-mediated increased FLAP mRNA expression occurred via activation of phosphoinositide-3 (PI-3) kinase, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, and hypoxia inducible factor-1alpha (HIF-1alpha). HIF-1alpha small interfering RNA (siRNA) reduced PlGF-induced FLAP expression. FLAP promoter-driven luciferase constructs demonstrated that PlGF-mediated luciferase induction was abrogated upon mutation of HIF-1alpha response element (HRE), but not the nuclear factor-kappaB (NF-kappaB) site in the FLAP promoter; a finding confirmed by chromatin immunoprecipitation (ChIP) analysis. PlGF also increased HIF-1alpha binding to the HRE in the FLAP promoter. Therefore, it is likely that the intrinsically elevated levels of PlGF in SCD subjects contribute to increased LT, which in turn, mediate both inflammation and AH. Herein, we identify a mechanism of increased LT in SCD and show HIF-1alpha as a hypoxia-independent target of PlGF. These studies provide new avenues to ameliorate these complications.
authors.affiliation: Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA.
authors.forename: Nitin
authors.initials: N
authors.lastname: Patel
authors.forename: Caryn S
authors.initials: CS
authors.lastname: Gonsalves
authors.forename: Minyang
authors.initials: M
authors.lastname: Yang
authors.forename: Punam
authors.initials: P
authors.lastname: Malik
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Kalra
mesh_terms: D058927:5-Lipoxygenase-Activating Proteins; D000755:Anemia, Sickle Cell / Q000150:complications / Q000378:metabolism*; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D002352:Carrier Proteins / Q000096:biosynthesis*; D002460:Cell Line; D002648:Child; D002675:Child, Preschool; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D015289:Leukotrienes / Q000096:biosynthesis*; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis*; D019255:NADPH Oxidases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000072483:Placenta Growth Factor; D011257:Pregnancy Proteins / Q000378:metabolism*; D012130:Respiratory Hypersensitivity / Q000209:etiology / Q000378:metabolism*; D020218:Response Elements
chemical_list: D058927:5-Lipoxygenase-Activating Proteins; C548592:ALOX5AP protein, human; D002352:Carrier Proteins; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D015289:Leukotrienes; D008565:Membrane Proteins; D016328:NF-kappa B; C000608036:PGF protein, human; D011257:Pregnancy Proteins; D000072483:Placenta Growth Factor; D001094:Arachidonate 5-Lipoxygenase; D019255:NADPH Oxidases; D019869:Phosphatidylinositol 3-Kinases